In a communication system including plural communication apparatuses that communicate each other using a single communication path, the state of the communication path is detected for communication. If the communication path is busy, a first control method is performed for controlling access to the communication path using a back off time selected at random. A second control method secures the communication path by transmitting and receiving the predetermined signal at transmission of a signal so as to control access to the communication path. In accordance with the kind of the signal to be transmitted, the first or the second control method is selected for communication. Thus, plural communication apparatuses can perform efficient communication.